It is known that .alpha.-keto acids and salts thereof are useful as starting materials in the production of herbicides. In particular, ar aqueous solution of the sodium salt of TMPA is used in the synthesis of the herbicide Sencor. In the prior art, various processes for producing .alpha.-keto acids and salts thereof have been proposed. These processes include (1) reacting sodium cyanide and acetyl chloride to form acetyl cyanide and then hydrolyzing the cyanide; (2) dry-distilling tartaric acid in the presence of potassium hydrogensulfate; (3) fermenting lactic acid; (4) oxidizing lactic esters with potassium permanganate; and (5) oxidizing propylene glycol.
In U.S. Pat. No. 4,175,188, a process is described for producing TMPA from trimethylpyruvic acid N-t-butylamide. The process includes the acid hydrolysis of trimethylpyruvic acid N-t-butylamide by heating under reflux in hydrochloric acid, and then extracting with dilute sodium hydroxide, hydrochloric acid and ethyl acetate. The yield of the desired product is only 75% of theory.
In U.S. Pat. No. 4,614,822, a process is described for preparing TMPA by oxidation of the corresponding .alpha.-hydroxy acid.
The above-identified processes have various disadvantages which include the following: (i) the yield of the desired product is low, and (ii) the formation of considerable amounts of by-products makes it difficult to separate and purify the desired product.